Modern mobile communication tends to provide a user with a high-speed transmission multimedia service. FIG. 1 shows a diagram of a long term evolution (LTE) system architecture.
In FIG. 1, a user equipment (UE) 101 is a terminal device for receiving data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network, including a macro base station (eNodeB/NodeB) that provides an interface for the UE to access a wireless network. A mobility management entity (MME) 103 is responsible for management of a mobile context, a session context, and security information of the UE. A serving gateway (SGW) 104 mainly provides a user plane function, which may be in a same physical entity as the MME 103. A packet data network gateway (PGW) 105, responsible for charging, lawful interception, etc, may be in the same physical entity as the SGW 104. A policy and charging rules function (PCRF) 106 provides a policy of quality of service (QoS) and a charging rule. A general packet radio service supporting node (SGSN) 108 is a network-node device which provides routing for data transmission in a universal mobile telecommunications system (UMTS). A home subscriber server (HSS) 109 is a home subsystem of the UE which is responsible for protecting user information that includes current location of the user equipment, an address of a serving node, user security information, a packet data context of the user equipment, and so on.
An object of a group communication service is to provide a quick and efficient mechanism and distribute same data to users in a group. A concept of the group communication has been widely used in a land mobile radio (LMA) system of a public security organization. A typical application is to provide a function of “push to talk” (PTT). When the group communication service is introduced into LTE, the group communication service in LTE at least supports a PTT voice call, and its performance is comparable to traditional group communication PTT performance. A group communication service in SAE needs to support the UEs in different states and different surroundings of the UEs. There is wideband data transmission in LTE, so the group communication service in LTE needs to support data communication such as voice, video, etc.
Group call system enabler (GCSE) in LTE means that a function of an application layer is introduced into 3GPP to support group communication. Users in LTE are divided into different groups. One user may belong to one GCSE group or a plurality of different GCSE groups. The user in the GCSE group that needs to receive GCSE service data is called a receiving group member, and the user for sending the service data is called a sending group member. The group communication is the communication between the sending group member and the receiving group member. In addition, it is also required to support the user to communicate with multiple groups at the same time. For example, the user makes a voice communication with a group, and makes a video communication or other data communication(s) with another group.
In order to utilize air interface resource effectively, in the case that multiple receiving users receive a same data service, the date service is provided to the user by adopting a broadcast and multicast way. Such service is called a multimedia broadcast and multicast service (MBMS). Each MBMS bearer provides the service in its own service area. In each cell of the service area, there is a dedicated control channel (MCCH) to transmit a MBMS signal. BM-SC is a center providing the multimedia broadcast and multicast service. MBMS data is sent from the BM-SC to MBMS-GW located between the BM-SC and an eNB that is a logical node or other network node. The MBMS-GW is responsible for sending/broadcasting a MBMS data packet to each eNB that is required to transmit the data. The MBMS-GW sends the MBMS data packet to a corresponding eNB which sends data to the user. A control signal is sent from the BM-SC to the MBMS-GW, and then sent to the EUTRAN through the MME. A MCE is a node of the EUTRAN, which receives the MBMS signal, determines to use a MBSFN transmission mode, and then sends the signal to the corresponding eNB. FIG. 2 is a schematic architecture diagram of an eMBMS. The MCE may be a single node, or together with the base station. The MBMS for LTE is called the eMBMS for short.
An eMBMS service may be transmitted in a single-carrier cell, so that different cells use different carriers, a cell-edge user can only listen to a current MBMS service of the cell. However, when a neighboring cell transmits a same MBMS service with a same carrier synchronously, the user in neighboring cell edge may receive a sum of the two signal energy. Therefore, in a prior art, a continued area is defined. In this area, each eNB transmits the same MBMS with the same carrier in the synchronous way to improve MBMS service receiving quality. The continued area is called a single frequency network (SFN) area which includes a group of cells whose geographic locations are continuous. These cells transmit a certain MBMS service in synchronization by using a same radio resource.
A GCSE service may be transmitted through an eMBMS bearer, but it can not meet requirements of the GCSE service just by using the existing eMBMS technology. For example, a data bearer is established with 300 ms as required by the GCSE service, but in the eMBMS technology, the MCE needs to transmit the signal to all eNBs within a scope of the MBSFN first, and then the eNBs transmit MBMS control information synchronously in the air interface. Required time in this process exceeds that of the GCSE service. Currently, two methods have been proposed to solve the problem. In the first method, the eMBMS bearer is established in advance. In the second method, a point to point bearer is established in the network first, and the data is sent to the receiving group member through the point to point bearer. At the same time, the eMBMS bearer begins to be established, and after the eMBMS bearer is successfully established, the data is sent to the receiving group member through the eMBMS bearer. Within a period of time, the data is sent on the point to point bearer and the eMBMS bearer simultaneously.
Although the above method can solve the time-delay problem of bearer establishment, based on analysis, it is discovered that the following problems need to be solved.
1) In a current eMBMS system, the eMBMS system is just used to send the MBMS service. When the service starts, the MCE may count the number of users, and determine whether to suspend or resume the data transmission according to the number of users. Specifically, when the number of users is less than a threshold value, the MCE determines to suspend the data transmission, so as to save the air interface resource and power consumption of the UE. Thus, the UE is unable to receive the eMBMS control signal and data. When the eMBMS system is used to transmit the GCSE service, the UE needs to establish a point to point channel for the GCSE service. In the establishment process, the UE cannot receive the data, which leads to interruption of the data transmission.
2) When the GCSE service needs to use the eMBMS bearer for transmission, a GCSE server can not whether the MCE has determined to suspend the data transmission.
3) Currently, only the MCE can make a decision to resume the MBMS data transmission.
4) A node is need to determined whether to send the CGSE service to the receiving group user through the point to point bearer or the MBMS bearer, and when to switch between the two bearers.
5) When the UE moves into a new cell, and the GCSE service is not provided by the new cell through the MBMS, the UE needs to establish the point to point bearer in the new cell, which leads to interruption of the data transmission.
6) When the UE moves into a new cell, and the GCSE service is provided by the new cell through the MBMS, the UE needs to listen to broadcast information, and then listen to the MBMS control information, so the UE can receive the GCSE service data, which leads to interruption of the data transmission.